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[snappyHexMesh] first cell height and mesh quality

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Old   October 1, 2021, 13:33
Default first cell height and mesh quality
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I'm trying to mesh a hull geometry but I can't seem to be able to create prism layers with first cell height 0.001m.

If I increase the first cell height (say to 0.007m) I get some layers.

If I turn off all quality controls in the meshQualityDict I get all the layers (and they look ok) but then the checkMesh fails.

I am using absolute sizes (relativeSizes false) and firstAndRelativeFinal for the thickness model.

I've also attached the checkMesh log file in which I notice the following three lines:

  <<Number of duplicate (not baffle) faces found: 32. This might indicate a problem.
  <<Number of faces with non-consecutive shared points: 32. This might indicate a problem.
  <<Writing 88 faces with non-standard edge connectivity to set edgeFaces

but I really don't know where to start looking in order to rectify anything that is implied as the underlying issue.

What am I missing?

I would appreciate any help.



    // Are the thickness parameters below relative to the undistorted
    // size of the refined cell outside layer (true) or absolute sizes (false).
    relativeSizes false;
    // thicknessModel keyword that can take the value of:
    // firstAndOverall;
    // firstAndExpansion;
    // finalAndOverall;
    // finalAndExpansion;
    // overallAndExpansion; or
    // firstAndRelativeFinal
    thicknessModel firstAndRelativeFinal;

    firstLayerThickness 0.001;

    // Wanted thickness of final added cell layer. If multiple layers
    // is the thickness of the layer furthest away from the wall.
    // Relative to undistorted size of cell outside layer.
    // See relativeSizes parameter.
    finalLayerThickness 0.5; //$fLayerThickness;

    // Expansion factor for layer mesh
    //~ expansionRatio 1.2;

    //  Overall thickness of the cells (size specification depends on the 
    //  relativeSizes parameter). 
    //  Ignored if using finalLayerThickness or firstLayerThickness.
    //~ thickness 1.5;

    // Minimum thickness of cell layer. If for any reason layer
    // cannot be above minThickness do not add layer.
    // See relativeSizes parameter.
    minThickness 1e-4;

    // Per final patch (so not geometry!) the layer information
            nSurfaceLayers 15;   
            //~ thicknessModel firstAndRelativeFinal;
            //~ firstLayerThickness 0.001;
            //~ finalLayerThickness 0.5;
            //~ thickness 0.2;
            //~ expansionRatio 1.2;
            //~ minThickness 0.0;
OF version is 2012
Attached Files
File Type: txt checkmesh.txt (6.9 KB, 1 views)

Last edited by Aeronautics El. K.; October 1, 2021 at 15:46.
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Old   October 10, 2021, 16:23
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ok, seeing that no one apparently has any clues to tackle the original question, I'll ask something (hopefully) easier.

Does anyone know which parameter in the meshQualityDict controls the maximum allowed aspect ratio of the cells?

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